Page:Tropical Diseases.djvu/988

930 T. equinum (Fig. 226), the cause of "mal de caderas" in South America, the kinetonucleus is very minute.

Trypanosomes occur as blood parasites in all classes of vertebrates. Many wild animals harbour small numbers of these parasites in their blood. Certain are specific and probably harmless to their particular vertebrate host.

Trypanosomes of cold-blooded animals include T. rajæ, T. damoniæ, T. granulosum, and T. rotatorium (Figs. 227-30).

Though showing but slight morphological differences as a general rule, members of this genus have been differentiated on morphological as well as on pathological grounds.

The Lewisi group includes T. lewisi, T. cuniculi, T. duttoni of the mouse, T. microti of Microtus arvalis, all about equal in size (24-25 μ in length and 1-2 μ in breadth), and similar in general appearances; that is, the organisms are long and slender; both the flagellar and aflagellar extremities are markedly pointed and the nucleus situated towards the flagellar end. They are non-pathogenic, or only slightly pathogenic.

The Brucei group includes nearly all the pathogenic varieties: T. brucei (nagana), T. gambiense (sleeping sickness), T. rhodesiense (human trypanosomiasis in Rhodesia), T. evansi